I just installed a 6-inch Skyjacker suspension lift on my 72 GMC Jimmy and am experiencing some unpleasnt side effects from the lift. I should mention, I went from a 4-inch lift with 33's and no problems to a 6-inch lift with 35's.

I am experiencing a high degree of bump-steer and wondering with the new lift. I did install an extended pitman arm, as well as a new adjustable drag-link. What is likely causing the bump-steer and wondering and how can I correct these unpleasant lift side effects?

How bad is the wandering and bump steer. With a lift your going to get some bump steer. Some things that you should check to make sure you have the drag link set to the correct length, and check your tie rod ends for any play. I put in a new gear box and changed out my tie rods and it made a big differnce in my truck. Oh BTW I have a 6" with 35's too. Oh yeah and check the steering arm for play.

I went from a stock pitman arm and draglink with a raised arm on the axle in my '70K5 with Rancho 4" springs to a raised arm and stock draglink and stock pitman arm with 6" ProComp springs on the '73 I traded for. In the '70 my draglink was flat to the axle arm and hadf no bump steer. In the '73 the draglink runs down to the axle arm and has bad bump steer on braking. I think I need a lowered pitman arm to fix this. And no comments about trading the 1st gen for the 2nd gen please, as both of us are happy at this time with the deal. /forums/images/graemlins/thumb.gif

i think to correct most steering problems,the drag link has to be parellel to the axle meaning if you look at it it has to be almost level.mine has a raised steering arm with 4 inch lift and it is really strait and i dont have much problems with steering.only on the highway when i hit the big ruts that the big trucks leave because they mostly drive in the right lane.i also have a single rancho stabilizer which helps quite a bit.

chulisohombre that's what I was trying to explain in my post. When the draglink was straight and level to the ground I had little or no bumpsteer. Now that the draglink runs down to the the axle under braking or anything that causes the spring to flatten it tries to push the wheel to one side or the other aka bumpsteer. If I add a drop pitman arm it'll cure most of this problem. I just have to deside if I want to spend that money now or start on going to crossover/ hyd. steering on the D44 in there now or do the pitman arm for now and go crossover/ hyd. when I go D60 in the front. Either way at some point it will be crossover/ hyd. /forums/images/graemlins/thumb.gif

hey yall, the problem is the moment arm. if you impart an angle (two axis) to the previously straight (one axis) steering arm by introducing an angled arm, you introduce a moment (force x displacement) on the link. this is why a drop arm is effective, since the moment in the sensitive axis is minimized by the drop. iow, it's a good as you can do without altering the location of the prime mover (the steering box). this may not be clear. just tell me if it is not.

Every company's lift is a little different, so the change in longitudinal displacement that accompanies the vertical displacment will be a little different. Sometimes, raised steering arms exacerbate the bump-steer problem because in keeping the drag link horizontal, the longitudinal displacement of the rear ball joint in the drag link is negative (toward the front of the truck) with any vertical displacement of the axle, while the axle will have positive longitudinal displacement under compression on a lifted truck. A correction for this would be an S-shaped drag link, which would roughly mimic the linear displacements of the axle. Fine-tuning using a raised steering arm may be necessary as well. Note that there are at least three different geometries of raised steering arms that I have seen on the market.

Crossover steering reduces bump steer due to the reduction in angular displacement per unit of vertical linear displacement. It does not completely get rid of bump steer, but it helps. The big problem with a crossover setup for those of us running Gen2 front anti-sway bars is collision of the drag link with the moment arms of the front bar. Some sort of convoluted drag link center section needs to be devised to clear the bar, but it'd have to be specific for each lift range and disconnect setup. I've got ideas in my head for the lift I'm planning on having on my Blazer and I'm probably going to fab something up once I have the lift on my Blazer.

dont quote me but i think a dropped pitman from skyjacker or someone is only 50 bucks.i cant remember where i seen it.if so it would be a good temporary fix for the problem and you can resell it later when you do crossover on the 44 or the 60.

sorry i must have coppied wrong.skyjacker part #CA50 for 2 inch drop pitman and is 59.95 from national tire and wheel. /forums/images/graemlins/thumb.gif.they also make a 6 inch raised steering arm with a part #CA150.whichever one you go with should work well.

i guess im just a idiot,sorry my brain is half mush.too many head injusries as a kid and they are finally ketching up to me.haha.i cant find a price for it but would you consider the 6 inch raised steering arm?it is part #CA150 from skyjacker.i think you would have to call to get a price.i cant find it online.i went to summits site.they have 3 or 4 listed but doesnt give a description of the pitman arm.they are under 60 bucks.they are from moog so i dont know if they make a dropped arm but like i said they had 3 or 4 different parts # for the same application.might be 2 wheel and 4 wheel application but who knows.it doesnt say.hope you finally find what you need.i would probably go with the 6 inch raised arm myself and just sell the steering arm you have now.i just cant find a price on it online.youd have to call somewhere and get a price for it.

My bumpsteer problem still persists with my 72-Jimmy since the addition of a 6-inch lift even though I have done the following:

1) Installed 4-inch raised steering arm

2) Installed new adjustable (straight not S-shaped) draglink.

3) Removed the degree shim on the bottom of the front spring packs to decrease castor angle while sacrificing drveline angle. (I can't accept not being able to anticipate how my truck will handle when driving down the road)

4) Had my buddy do an alignment and we improved the castor angle by removing the front spring pack shims and also correct toe.

Things I will now try:
1) Install a 2-inch drop pitman arm

2) ?????

Any thoughts you have are greatly appreciated. I have made some progress but not enough to feel comfortable taking my family in the rig or jeopradizing other motorists.

Looks like you may have already addressed this but here is my thought. After experiencing bump steer after installing a 4" Skyjacker lift on my "72 K-5, I went through all of the troubleshooting to try to correct it. I already had the raised steering arm so started at the alingment shop. Turns out my castor was only about -2 degrees. Stock for a '72 is -4 degrees. In 1974 or so they changed to -8 degrees. As you know, cars have positive castor with the smaller tire and lower clearance, it makes it much easier to turn the wheel. As you increase to negative castor, it takes more force to turn the wheels. This is why they use negative castor on trucks with a taller center of gravity and bigger tires. More force to turn the wheel equals more stability on the road. Anyway, I theorized that my low degree of castor was to blame for my bumpsteer so I purchased a later model front diff with the -8 degrees to swap in. Unfortunately I sold the vehicle before I swapped it so I can't tell you if that cured it or not. I'm thinking it definitely would have. Unfortunately swapping the diff is the only way to correct the castor and still maintain acceptable driveline angle unless you want to cut off your knuckles and correct it that way. What is your castor angle? Maybe all of this advice means nothing if your already in the -6 to -8 degree range. Good luck. Keep us up to date on your progress.

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